1. Field of the Invention
This invention relates to electric welding and, more particularly, to a torch for gas-shielded arc welding in a narrow deep groove.
2. Background Art
Known in the art is a torch for gas-shielded arc welding in a narrow deep groove, comprising a current contact torch bit featuring an electrode set normally to the welded surface, and two nozzles, one nozzle being placed before and the other after the electrode as the latter travels in relation to the workpiece.
The torch bit, nozzles and groove walls produce an enclosed volume around the electrode, which is filled with shielding gas (cf., French Pat. No. 2,272,781, filed 1976). Such design of a torch provides for good gas shielding only when the electrode is set normally to the workpiece surface. If this torch uses a tilted electrode of an extended free length, the gas shield deteriorates substantially. Moreover, the known torch has its nozzles periodically blocked up by molten metal splatter.
Also known is a torch for gas-shielded arc welding, comprising a current contact torch bit with an electrode and an O-shaped nozzle having double walls, the space between sald walls being communicated with a gas-feeding tube. The top portion of the outer nozzle wall features several horizontally arranged holes. The torch tip and the nozzle are introduced into the groove, the nozzle being positioned above the arc so that the axis of the nozzle and the axis of the tilted electrode intersect at the groove bottom. The arc is shielded by a flow of gas escaping from the nozzle. The gas flow is protected against injecting air intake by carbon dioxide fed from a hole at the top of the nozzle (cf., the USSR Inventor's Certificate No. 566,432, Aug. 13, 1975).
This torch is also insufficiently protected in the arc and weldpool zone because the flow section of the nozzle tends to grow smaller due to sticking of metal drippings. Clusters of splatter can also fall into the weldpool and cause weld defects, the welding process has, therefore, to be stopped periodically to clean the torch. Besides, the nozzle being positioned above the arc, the position of the electrode in the groove in relation to the edges is difficult to watch.